JAKARTA, Dec 10 (Reuters) - Southeast Asian stock markets closed mostly lower on Thursday as concerns over global economic growth persisted, with Malaysia posting its biggest single-day percentage loss in a month. Malaysia's main stock index fell 0.7 percent, its lowest closing level since Oct. 5. Electricity producer Tenaga Nasional Bhd dropped 1.1 percent, among the biggest losers on Thursday. "Given the absence of window-dressing, bearish technical momentum and slumping oil prices